In her geometry class, Gabriela took 5 tests. Her scores were 77, 86, 98, 85, and 89. What was her average score on the tests?
The average is the sum of her scores divided by the number of scores. There are 5 scores and their sum is $77 + 86 + 98 + 85 + 89 = 435$ Her average score is $435 \div 5 = 87$.